How to seal an art canvas

Sue SteppUpdated February 21, 2017

Sealing art canvas keeps it preserved for a long time. Art canvas is sealed before and after applying painting to the material. A layer of sealant is applied to unfinished canvas that protects the material from damaging chemicals and moisture. After a painting is completed, a layer of sealant keeps dirt, dust, debris and moisture from damaging the completed artwork. Different types of paintings on canvas require different sealants.

Paint a layer of gesso or white acrylic paint on the canvas before painting with oil paint, acrylic or watercolour. This protects the cloth from damaging chemicals used in some painting processes. White acrylic paint works as a substitute for gesso, even though gesso is the preferred sealant for canvas.

Allow the first layer of gesso or acrylic paint at least three hours for drying. If you apply a second layer before the first layer is fully dried, it leaves an ugly texture on the canvas.

Paint a second layer of gesso or acrylic paint on the canvas, and let it dry fully. The canvas is ready for painting after a full 12 hours of drying.

Spray a light coat of workable fixative over a pastel drawing between layers, so the design underneath doesn't get smudged or damaged. The workable fixative darkens the colour of the pastels, so use very thin layers. Keep the spray can at least 12 inches away from the canvas as you spray on the workable fixative.

Let the workable fixative dry for at least one hour before adding more pastel. You may add several layers of colour between layers of workable fixative.

Cover the finished pastel painting with a light coat of spray fixative for pastel paintings. Do not use hairspray because it causes a dull, yellow film on the painting after a few years. Let it dry for several hours before hanging or framing.

Check that the painting is completely dry before sealing the canvas. If the paint is wet, mould develops under the sealant.

Spray on three thin layers of clayboard fixative across a watercolour painting or paint on three thin layers of gloss gel medium on acrylic paintings, allowing at least one hour for drying time between each layer. The fixative keeps the paint from running, and gives it a protective coating.

Apply the triple thick glaze spray in a thin layer across the canvas once the clayboard fixative or gloss medium is dry. Put on one coat for a light, glossy finish, or let it dry and add a second coat for a high-gloss finish.

Wait six months before sealing an oil painting on canvas. Oil paint takes a minimum of six months before the paint dries.

Wipe the surface of the painting gently with a damp cloth. This removes any dust or debris from the surface.

Paint a thin coat of the retouch varnish over the whole painting. With this varnish, the paint under the varnish continues drying. It protects the painting, but dust collects on it easily.

Spray on a thin coat of dammar spray varnish after one year. After one year, the painting is dry enough for a permanent spray varnish. It doesn't matter what brand of dammar varnish you use because they all work well. This completely seals the painting, so it is easily cleaned without damaging the painting.